1. Field of the Invention
The invention relates to an improved process and apparatus from which a sample is extracted under conditions of high temperature and high pressure.
2. Description of the Related Art
It is known that an extractor of the type known as 10 Soxhlet can be used for the multiple extraction of samples, whereby the solvent can be distilled off and the desired substance(s) can be extracted from the sample in a continuous cycle.
There are such devices in which the distillation and extraction take place at normal (ambient) pressure or at elevated pressure (high-pressure extraction).
A device of the above referred to type is familiar as a one-piece glass molded article, which consists of an upper glass flask for the samples and a lower glass flask for the solvent, and two separate external connection tubes that connect the lower and upper glass flasks together. One of the connection tubes is a vapor tube, which branches off from the lower glass flask and leads into the upper glass flask near the top thereof. The other connection tube is an overflow tube which starts from the lower part of the upper glass flask, extends upwards in it up to a certain level, and then leads down into the lower glass flask.
This known device is expensive, in relation both to its construction and to the procedures that can be carried out with it. Heating of both the solvent and the sample material is difficult, firstly because the heat from a heat source, for example a Bunsen burner, is not easy to transfer to the materials being heated, and then because glass, as a construction material, is a poor conductor of heat. As a rule, this known device is only made in relatively small sizes, so that only small extraction jobs can be carried out. A further disadvantage of the known device is that since it is made of glass, it is very sensitive and can break easily.
A high-pressure extraction device is described in USA 4 265 860 or in DE A1 4 114 525.9. In this known device the extractor is housed in a pressure-tight housing with a charging opening closed off by a cover. During operation of the device, distillation of the solvent increases the pressure in the pressure vessel, which causes the boiling point of the solvent to rise and so increases the working temperature. This substantially enhances the performance of the device, and in addition the elevated pressure favors the extraction of the samples because the solvent can penetrate better into the sample material.
In addition, in the device known from DE,A1, 4 114 525.9, two receptacles are provided in the pressure vessel, namely one solvent container made of plastic lining the inner wall of the metal pressure vessel, and inside and concentric with that, a glass sample container resting on a shoulder and fitted with an external overflow pipe connected in one piece with the sample container. The sample container is arranged a certain distance above the bottom of the solvent container, supported by a circular flange that rests against an interior shoulder of the solvent container. The solvent and sample materials are heated by microwave radiation admitted via an opening at the bottom of the pressure vessel covered by a material transparent to microwaves. When the solvent evaporates, the vapor passes upwards into the annular space between the solvent container and the sample container, and through holes in the circular flange into the vapor space over the sample container. In the area of the vapor space, the pressure vessel is surrounded by a cooling device formed by an annular water pipe in the peripheral wall of the pressure vessel and therefore in direct contact with the upright wall thereof. Over the sample container is a perforated screen over which the solvent condensed by the cooling device against the upright inner wall flows and falls into the sample container.
In WO 93 22650 devices for the vaporization or drying and extraction of samples are described in several design variants (see FIGS. 1 to 23). In these design examples, the inside of at least one container for receiving and treating the sample is connected to a suction device by means of one suction pipe, and by means of a common or two separate inlet pipes to a flushing gas supply device and/or a supply device for a reagent or solvent. During the vaporization treatment, the vapors given off when the sample is heated are continually extracted by the suction device, producing an underpressure in the container which lowers the boiling and evaporation points of the reagent, so that the sample can be treated at a lower temperature. This is especially advantageous when the sample material and/or the reagent medium must not be treated at higher temperatures, which they may not tolerate for example.
FIG. 24 of this specification shows a device for the preparation of samples under the action of heat and elevated pressure.